Fujitsu Corporation

Hiroya Egoshi

Kazuhiro Kunimatsu

Takeshi Ono

Shinichi Takeda

Yoshinobu Matsukawa

Akio Takayasu

Tadashi Soga

Yukiko Miyazaki

The present invention relates to a wavelength multiplexing apparatus for multiplexing and/or demultiplexing a plurality of optical signals in the wavelength region and a signal conversion apparatus for interfacing a transmission line corresponding to any of the optical signals with the wavelength multiplexing apparatus. By using these apparatus according to the invention, the signal to be a reference for synchronization between the wavelength multiplexing apparatus and the signal conversion apparatus is reliably delivered via an existing optical transmission line therebetween, without the reduction of transmission quality and the limitation on modulation systems. Therefore, in an optical transmission system with the present invention applied thereto, it is possible to meet conditions for office establishment and arrangement of the apparatus and satisfy the demands for maintenance/operation flexibly and at a low cost. Further, service quality and reliability are maintained at high levels.

Wavelength multiplexing apparatus and signal conversion apparatus

An apparatus having n-number of working cross-connects for cross-connecting an n-bit input signals arriving from a plurality of input paths on a per-bit basis; n-number of first logic circuits for calculating the exclusive-ORs of each said n-bit and applying outputs to a standby cross-connect for providing outputs; n-number of second logic circuits for calculating the exclusive-ORs of said output signals from each of said working cross-connects and from the single standby cross-connect; and third logic circuits for selecting output signals of said working cross-connects and outputs of the second logic circuits. The apparatus detects the occurrence of an abnormality in working cross-connects by monitoring the outputs of the second logic circuits, identifies the faulty cross-connect by successively turning off one of the n-inputs to the first and second logic circuits, and select outputs from the second logic circuits instead of from the faulty cross-connect by using the third logic circuits.

Cross-connect apparatus

A transmission system having an uninterrupted switchover function for a plurality of lines is disclosed. The aims are to prevent unnecessary switchover and to provide high quality transmission system even using low quality lines with a minimal hardware configuration of memories and a control circuit. On the transmitting side, a pulse for phase synchronization is inserted at the top of each signal frame. Such frame signals are branched to transmit on a plurality of lines. On the receiving side, an alarm or error in signals from lines is detected on a frame basis. Then, a line switchover is carried out at the unit of a frame after frame phases are synchronized. To synchronize the frame phases, elastic memories for producing variable amount of delay are used in addition to fixed-amount delay circuits. This enables to insert a sufficient amount of delay to generate required timings for detecting errors, controlling and performing a switchover etc. Namely, time margin needed from the detection of an alarm or error to the execution of switchover is produced. Consequently, before the signal having an alarm or error is output, the line can be switched over without producing momentary interruption against signal traffic.

Transmission system having an uninterrupted switchover function for a plurality of lines

A transmission system for transmitting data of a synchronous digital hierarchy SDH frame includes a transmission terminal, a transport terminal and a reception terminal linked together by a working channel line and a protection channel line in a redundant structure. Each of the transmission terminal and the transport terminal includes an alarm indication insertion unit which inserts an alarm indication in the SDH frame, the alarm indication indicating whether a related channel line has failed. The SDH frame containing the alarm indication is transmitted to the reception terminal prior to transmission of the data on the related channel line. The reception terminal includes a control unit which outputs a selected one of the SDH frame on the working channel line and the SDH frame on the protection channel line in response to the alarm indication received by the control unit. When one of the working channel line and the protection channel line has failed, the control unit switches a connection from one of the working channel line and the protection channel line to the other without causing instantaneous cutoff.

Transmission system for switching connection from a working channel line

An apparatus for establishing synchronization between transmission signals transmitted from a signal source of a sending end to a receiving end via regular and alternative lines in a network using a transmission system such as the SDH and SONET. In the sending end, the present invention inserts a FP signal in the multiplexed information of the signal output from the signal source. On both regular- and alternative-line sides of the receiving end, it detects the pointer in the transmission signals received from the respective lines, separates the multiplexed information from the transmission signal based on the pointer, stores the separated multiplexed information in a memory unit which is capable of varying its storage capacity as specified and reading out the information when a time corresponding to the storage capacity has elapsed after the information is stored, outputs a detection signal when the FP signal is detected in the multiplexed information output from the memory unit, and specifies the storage capacity of at least one of the memory units so that the detection signals occur at the same time.

Apparatus and a method for establishing signal synchronization between

A system for controlling signal transfer between a plurality of devices, for controlling the transfer of signals between a main device having processors packaged therein and a subsidiary device having units packaged therein, includes a multiplexer section on the main device side for multiplexing signals from a control system processor and a monitor system processor of the main device; a demultiplexer section on a subsidiary side for demultiplexing the multiplex signal from the multiplexer section on the main device side and distributing it to the units of the subsidiary device; a multiplexer section on the subsidiary device side for multiplexing the signals from the units of the subsidiary device; and a demultiplexer section on the main device side for demultiplexing the multiplex signal from the multiplexer section on the subsidiary device side and distributing it to the control system processor and the monitor system processor. The multiplexer section on the main device side executes bit-stuffing and multiplexing in such a manner as to correspond to the phase or frequency difference between clock signals from clock generators and transfers the signal to the subsidiary device through a cable.

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Kawasaki, Japan

Hiroya Egoshi